PROJECT SUMMARY Cognitive bias towards alcohol, or the automatic tendency to visually focus on and approach alcohol cues, has been used to predict alcohol onset and increases in alcohol use among underage drinkers. It is believed to arise when situational alcohol cues are repeatedly paired with rewarding alcohol use experiences, sensitizing individuals to these alcohol cues. Existing research demonstrated that bias is associated with alcohol use in youths, who are very sensitive to reward and experience the greatest increases in alcohol use onset and dangerous drinking levels. However, cognitive bias was largely investigated using single, laboratory-based, assessments. This approach overlooks important questions about the within-person variability of cognitive bias and its interaction with the social and environmental context. Specifically, adolescent and young adult drinking is largely a social affair, taking place in familiar environments, and cognitive bias is expected to be strongest when in the same social and physical environment that adolescents are ordinarily in. Furthermore, initial alcohol use has been shown to increase cognitive bias, and is expected to exacerbate the link between cognitive bias and alcohol use by disrupting regulatory processes. It also offers additional alcohol cues eliciting further cognitive bias. Moreover, studies examining the effect of acute alcohol on cognitive bias have been limited to administering alcohol to participants of legal drinking age. Because of this, a key developmental period of heightened alcohol use and reward sensitivity is missed. The proposed study?s use of momentary assessments of cognitive bias, context and alcohol use allows us to assess acute alcohol effects on cognitive bias in an underage population. The proposed study uses electronic diaries to assess whether cognitive bias is greater on drinking days, whether it predicts greater drinking on those days, and whether context heightens the effect of cognitive bias on drinking. Males and females who indicate weekly alcohol use (180 participants; ages 18-20 years) will complete standard human laboratory assessments of cognitive bias at baseline, and also 17 days of momentary assessments in daily life. These momentary assessments take place three times daily (at around 8-10am, 2-4pm and 7-9pm), as well as after the participant?s first drink. The proposed study offers to gather innovative data that is poised to answer important questions on when, where, and how cognitive bias leads to greater alcohol use. Future studies seeking to ultimately capitalize on the within-person changes and flexibility of cognitive bias among underage drinkers would greatly benefit from this innovation, because it would inform them on when and where to intervene.